Improvement in preventing the corrosion of iron and steel



UNITED STATES PATENT OFFICE.

'ROBERT A. FISHER, OF SAN FRANCISCO, CALIFORNIA.

IMPROVEMENT IN PREVENTING THE CORROSION OF IRON AND STEEL.

Specification forming part of Letters Patent No. 145,496, dated December 16, 1873; application filed July 28, 1873.

To all whom it may concern:

' the city and county of San Francisco, State of Galifornia, have invented an improved method of preventing the welLknown oxidation, corrosion, or wasting away of iron and steel ships by bilge-water, and of steam-boilers, iron tanks, and other forms of iron and steel used in commerce, manufactures, and the arts, in contact with natural waters, or aqueous solutions of matters soluble in water; and I do hereby declare the following description to be suiiicient to enable any person skilled in the art or science to which it most nearly appertains to make and use my said invention or improvement Without further invention or experiment.

My invention consists in employing a metal or combination of metals that, in contact with sea-water or other natural waters, or certain aqueous solutions, are more easily corroded, eroded,'or otherwise acted upon by oxygen, chlorine, or other corroding substances, than iron or steel is under the same circumstances, and hence the iron and steel are prevented from corrosion at 'the expense of the more easily corroded metal.

Aluminum, cadmium, magnesium, and zinc maybe used in connectionwith mercury; but in most cases I prefer an amalgam of zinc and mercury, or a solution of mercury containing more or less zinc, according to the temperature or character of the water or aqueous vsolution in contact with the iron or steel intended to be preserved from corrosion.

It will be seen that the above metals belong to the class that forms oxides insoluble in water. I am aware that the oxides of potassium and sodium (soluble in water) will prevent oxidation of iron; and I do not claim the use of them for such purpose.

I In illustration of one method of applying my invention, it may be stated that, if an iron pot,free from rust, be filled with sea-water, that part of the pot in contact with the liquid w ll soon begin to corrode, and the corrosion will rapidly continue, either at ordinary temperatures or at the boiling-point of the liq uid; nor will such corrosion be lessened by placing any amount of pure quicksilver in contact with the bottom of the vessel; but, if a small piece of perfectly clean zinc or zinc amalgam be placed upon the quicksilver, (mercury,) the rusting of the iron will be arrested until the-zinc has been entirely converted into the oxide of zinc or other compounds of that metal, and the proper chemical tests will show the absence of any iron in solution in the liquid.

My invention contemplates the renewal o zinc before the quantity originally used has been entirely oxidized or otherwise consumed.

The amalgam metal or alloy employed to prevent corrosion of steam-boilers, tanks, or any other form of iron or steel, while in contact with a corroding liquid, is not necessarily to be placed upon the 'bottomof the containing-vessel; nor is it requisite that in all cases it should be brought in direct contact with the metal to be protected. Under certain circumstances, it may be advantageous to place the more easily corroded material in a separate metallic pan, cup, or suitable contrivance, or upon a metallic shelf or ledge, or to use some other method of anaintaining metallic contact with the corroding liquid, the metal to be protected, and the material employed for such protection.

My invention has in view preventing corrosion of ships cables, and other forms of iron or steel stowed away in contact with fresh or sea water or other corroding liquid, and, when the application is practicable, of preventing the corrosion, or wasting away, or solution, of the iron or steel parts of vessels or machines, of any and every kind, constructed partly, as well as wholly, of steel or iron, and employed in contact with fresh or sea water, or aqueous solution, or corroding liquids, in commerce, or any proccssused in arts, manufactures, and mines.

I am aware that the principle of protecting -different metals from corrosion by means of galvanic action is old. I am also aware that,

to accomplish the same purpose, prepared iron has been covered or coated with a triple alloy, formed of zinc, mercury, and sodium or of which is insoluble in Water subsfiantially as potassium; but this I do not claim. above set forth. Having thus described my invention, what I In witness whereof I hereunto sch my hand claim, and desire to secure by Letters Patent, and seal.

The method herein described for protecting ROBERT FISHER iron against corrosion, consisting in the use Witnesses:

of a mercurial solution or amalgam of alumi- JOHN L. BooNE,

num, cadmium, magnesium, or zinc, the oxide 0. M. RICHARDSON 

